When wearing soft type contact lenses repeatedly over a designated period such as several weeks or months, it is necessary to periodically implement a sterilization process on the contact lenses. This is to maintain a safe and comfortable wearing state by preventing eye infections and eye damage due to microorganisms such as bacteria, mold or the like.
However, though disinfection by boiling is known as one type of sterilization process for contact lenses, in the case of soft contact lenses, there are cases when degradation of the lens itself or thermal metamorphism of adhered substances become a problem. Furthermore, a special device is needed for the boiling disinfection process, and the work is troublesome, so a non-heating type disinfection method has been used for the soft contact lens sterilization process instead of boiling disinfection.
As this non-heating type disinfection method, typically known are an MPS method with which the contact lenses are stored in a disinfectant solution of polidronium chloride, and a hydrogen peroxide method with which the contact lenses are immersed in a hydrogen peroxide solution to neutralize them. For example, this is as noted on pages 320 and 323 of the Japan Patent Office Standard Technology Collection “Glasses” (Non-Patent Document 1).
However, even with these non-heating disinfection methods of the MPS method and the hydrogen peroxide method, it was still difficult to say that sufficient sterilizing action is exhibited on the soft contact lenses.
Specifically, with the former MPS method, to realize a simple operation that makes it possible to perform the washing, rinsing, disinfecting, and storage which constitute the care for soft contact lenses consistently using one solution for all of them, a solution that does not have a sufficient disinfecting or sterilizing action is used. Because of that, there is the problem that it was difficult to say sufficient sterilization effect is exhibited. This issue is also mentioned in for example the National Consumer Affairs Center of Japan paper, “Disinfection Performance of Soft Contact Lens Disinfectant on Acanthamoeba” (Non-Patent Document 2).
Meanwhile, with the latter hydrogen peroxide method, to avoid an adverse effect on the ocular tissue by hydrogen peroxide solution that has adhered to the contact lenses, simultaneous with the start of the sterilization process by immersing the contact lenses in hydrogen peroxide solution, the neutralization process is actively implemented using a catalyst or neutralizing solution. Because of that, by immersing the contact lenses in water after the hydrogen peroxide solution is neutralized, there was the risk that bacterial contamination would occur after neutralization.